Imaging of Melting and Crystallization of Poly(ethylene oxide) in Real-Time by Hot-Stage Atomic Force Microscopy

Pearce, R.; Vancso, Gyula J.

doi:10.1021/ma970463y

Cited by 116 publications

(88 citation statements)

References 26 publications

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“…The bright lines in the images (Fig. 2C) are consistent with those of a typical morphology common in lamellar structures (38); for thick specimens of stacked lamellae, moiré fringes may also contribute to the contrast. Because DF imaging is very sensitive to changes in structural order (lamellar crystallinity and orientation), the intensity variation in the images taken at different times is a complementary indication of the structural change.…”

Section: Structural Dynamicssupporting

confidence: 80%

Macromolecular structural dynamics visualized by pulsed dose control in 4D electron microscopy

Kwon

Ortalan

Zewail

2011

Proc. Natl. Acad. Sci. U.S.A.

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Macromolecular conformation dynamics, which span a wide range of time scales, are fundamental to the understanding of properties and functions of their structures. Here, we report direct imaging of structural dynamics of helical macromolecules over the time scales of conformational dynamics (ns to subsecond) by means of four-dimensional (4D) electron microscopy in the single-pulse and stroboscopic modes. With temporally controlled electron dosage, both diffraction and real-space images are obtained without irreversible radiation damage. In this way, the order-disorder transition is revealed for the organic chain polymer. Through a series of equilibrium-temperature and temperature-jump dependencies, it is shown that the metastable structures and entropy of conformations can be mapped in the nonequilibrium region of a "funnellike" free-energy landscape. The T -jump is introduced through a substrate (a "hot plate" type arrangement) because only the substrate is made to absorb the pulsed energy. These results illustrate the promise of ultrafast 4D imaging for other applications in the study of polymer physics as well as in the visualization of biological phenomena.materials | polymers | biopolymers M acromolecular structural dynamics, unlike those of small molecular systems, involve complex free-energy landscapes with numerous possible conformations (1, 2). A prime example is that of protein folding that occurs as a result of a search from a high-entropy state of many conformations to the low-entropy native structure (3-5). This process is best described by the balance between the entropic and enthalpic free-energy contributions, as well as the "diffusion" through a multitude of energy barriers that form nucleation centers or misfolded structures on the path to the final state. The behavior has been likened to phase transitions, and in this regard it is also applicable to other large systems including organic polymers (6-8).In the transition, these macromolecules maintain the constituents or sequence of repeating units, but the conformations must undergo rearrangements from, for example, folded chains to random coils or extended chains (9). It is, therefore, important to understand conformational dynamics of macromolecules, biological (10) or abiological (11), and to elucidate the nature of the free-energy landscape that exhibits the multiple metastable states that are separated by entropic and enthalpic barriers. Visualization of the structures can be achieved using both real-space and diffraction imaging of electron microscopy, but these macromolecules are organics with facile bonds and, thus, probing of their motions represents a real challenge because of radiation damage. Moreover, the probing must span the time scales involved, from ps for rotational orientation to ns and microsecond (μs) for barrier crossings, and to hundreds of ms for refolding into the native structure.Here, we report real-time visualization of helical-macromolecular dynamics using diffraction and real-space imaging methodology of four-dimen...

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Section: Structural Dynamicssupporting

confidence: 80%

Macromolecular structural dynamics visualized by pulsed dose control in 4D electron microscopy

Kwon

Ortalan

Zewail

2011

Proc. Natl. Acad. Sci. U.S.A.

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“…Several groups have studied the crystallization behaviors and structures of semicrystalline polymers confined to nanoscopic spaces 1–3, 10–33. Frank and coworkers1–3 reported the substantial reduction of the crystallization rate in ultrathin films of poly(di‐ n ‐hexylsilane).…”

Section: Introductionmentioning

confidence: 99%

Lamellar arrangements of linear polyethylene in ultrathin films

Woo

Park

Jeong

et al. 2011

J of Applied Polymer Sci

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The crystal orientations of linear polyethylene films on silicon substrates are investigated using grazing incidence X-ray diffraction and atomic force microscopy. From diffraction analysis, we can identify the structural arrangement of PE crystals in ultrathin film. The orientation of lamellar crystal in PE films changes from edge-on to flat-on with the decrease of film thickness in the film thickness below $ 100 nm. The slightly inclined lamellae relative to the substrate are found to coexist with the flat-on lamellae in thin PE films that we have investigated. We find that the crystal orientation and structures is governed by the constraint imposed by film thickness rather than enthalpy gain as the film got thinner especially in the thickness below 200 nm.

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“…Most of the AFM studies related to the development of the morphology in polymer systems are performed at room temperature [6][7][8]. Recently, some appealing investigations have shown that using intermittentcontact mode AFM equipped with a hot-stage, it is possible to follow, e.g.…”

Section: Introductionmentioning

confidence: 99%